1. Field of the Invention
The present invention relates to fabrication of a microelectromechanical system (MEMS) device, and in particularly to a method for fabricating a MEMS device capable of preventing dielectric or metal layers of micromachined structures therein from damages.
2. Description of the Related Art
Microelectromechanical structures (MEMS) have found applications in inertial measurement, pressure sensing, thermal measurement, micro-fluidics, optics, and radio frequency communications, and the application field for these structures continues to grow. Conventional microelectromechanical structures, such as accelerometers, pressure sensors, flow sensors, microactuators and the like, typically comprise suspended micromachined structures having a released portion spaced apart from a substrate and one or more posts attached the substrate.
Generally, during fabrication of the micromachined structures, an uppermost patterned metal layer is used as an etching mask and an adequate etching process is performed to remove films not covered by the patterned metal layer to thereby form the micromachined structure.
Nevertheless, in the above etching process, since the patterned metal layers show limited etch resistance during the etching process, the obtained micromachined structure may not be formed in a desired profile. Thus, portions of the film layers in the micromachined structure may be partially or entirely removed during the etching process, thereby negatively affecting functionality of the obtained MEMS device.